1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and methods for expanding a tubular in a wellbore. More particularly, the apparatus and methods relate to an assembly for expanding a tubular into engagement with a downhole tubular. More particularly still, the apparatus and methods relate to a bottom hole assembly having an expandable tubular, an expansion member and an anchor configured to affix the expanded tubular to a downhole tubular.
2. Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed using a drill bit disposed at a lower end of a drill string that is urged downwardly into the earth. After drilling to a predetermined depth or when circumstances dictate, the drill string and bit are removed and the wellbore is lined with a string of casing. An annular area is thereby formed between the string of casing and the formation. A cementing operation is then conducted in order to fill the annular area with cement. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas or zones behind the casing including those containing hydrocarbons. The drilling operation is typically performed in stages and a number of casing or liner strings may be run into the wellbore until the wellbore is at the desired depth and location.
The casing may become damaged over time due to corrosion, perforating operations, splitting, collar leaks, thread damage, or other damage. The damage may be to the extent that the casing no longer isolates the zone on the outside of the damaged portion. The damaged portion may cause significant damage to production fluid in the zones or inside the casing as downhole operations are performed. To repair the damaged portion, an expandable liner may be run into the wellbore with an expansion cone. An anchor temporarily secures the liner to the casing. The expansion cone is then pulled through the liner using a hydraulic jack at the top of the liner. The hydraulic jack pulls the expansion cone through the liner and into engagement with the damaged casing. Thus, the liner covers and seals the damaged portion of the casing.
The hydraulic jack is limited in the amount of force it can apply to the expansion cone. Typical hydraulic jacks are limited to 35,000 kilopascal (kPa) applied to the work string. This limits the amount of expansion force applied to the expansion cone and thereby the tubular. Further, the hydraulic jack requires a high pressure pump to operate which adds to the cost of the operation. Moreover, the hydraulic jack must be located on top of the liner in order to pull the expansion cone. The location of the hydraulic jack makes it difficult to pump fluid down to the expansion cone in order to lubricate the cone during expansion. Still further, the hydraulic jack has a very small and limited stroke. Thus, in order to expand a long tubular, the hydraulic jack must be reset a number of times and pull the cone the length of several strokes of the jack.
Therefore, there exists a need for a mechanical expansion system capable of expanding a tubular with an increased force for an increased distance.